1. Field of the Invention
The present invention relates to a grid interconnection device and a power control system configured to control a backward flow toward a power distribution system.
2. Description of the Related Art
Nowadays, there have been increasing cases where a power supply device is provided in a customer (for example, a house and a factory) supplied with alternating current power from a substation. The power supply device is, for example, a photovoltaic power generator, a fuel cell power generator, or a secondary battery, and is connected to a power distribution system under the management of the substation through a grid interconnection device. Output power outputted by the power supply device is not only consumed by a power consumption device provided in the customer itself but also may be reversely supplied toward the power distribution system through a grid interconnection point between the grid interconnection device and the power distribution system.
However, if a backward flow from the customer to the power distribution system increases, the voltage of the power distribution system might exceed the upper limit of a voltage management range. In this case, the grid interconnection device in each customer alternately performs power system separation processing to disconnect the connection between the power supply device and the power distribution system, and interconnection processing to connect the power supply device and the power distribution system. For this reason, an excessive load is imposed on the grid interconnection device, and a situation in which a backward flow is not allowed frequently occurs.
To cope with this, proposed is a grid interconnection device provided to a customer and having a function of detecting a backward flow from another customer adjacent to the customer (see Japanese Patent Application Publication No. 2006-180660). The grid interconnection devices of the respective customers adjacent to one another simultaneously perform the power system separation processing and the interconnection processing, and thereby can prevent the voltage of the power distribution system from exceeding the upper limit of the voltage management range.